1. Field of the Invention
The present invention relates to an intake air routing device having a plurality of intake passages and a partition wall for partitioning intake passages from each other, and to an engine incorporating the same. More particularly, the present invention relates to an intake air routing device having a partition wall extending in an air chamber thereof by a predetermined length beyond upstream ends of the intake passages, and to an engine incorporating the same.
2. Description of the Background Art
There is a known intake air routing device having a plurality of intake passages for supplying intake air to respective cylinders of an internal combustion engine having a plurality of cylinders. An example of such known intake air routing device is disclosed in the Japanese Patent Document JP-A No. 1-208559 (particularly in FIG. 3 thereof).
As shown in FIG. 3 of the Japanese Patent Document JP-A No. 1-208559, an intake air routing device (18) for supplying intake air to an internal combustion engine having two cylinders (parenthesized numbers represent reference signs shown in the Japanese Patent Document JP-A No. 1-208559; some element names were changed and the same applies hereinafter) includes clean chambers (29A, 29B) partitioned from each other by a partition wall (28). The intake air routing device (18) is provided with an air chamber function serving as an air reservoir of the intake air.
In the intake air routing device of the Japanese Patent Document JP-A No. 1-208559, the clean chambers (29A, 29B) are completely partitioned from each other by the partition wall (28). With the clean chambers (29A, 29B) completely partitioned from each other, a phenomenon of mutual influence of intake air (hereinafter, referred to as “intake interference”) flowing through intake pipes extending from each of cylinders is eliminated. The phenomenon is caused due to a difference in intake timing between the cylinders.
However, depending on the engine displacement, there is a need to increase capacity of the clean chamber per cylinder in order to secure air volume of respective cylinders. Consequently, there was a possibility of increasing the size of the intake air routing device as a whole.
It is one of the objects of the present invention to provide a technology capable of reducing intake interference while suppressing an enlargement of intake air routing device for supplying intake air to an internal combustion engine having a plurality of cylinders.